Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-6985 is a medium-severity Improper Resource Shutdown or Release (CWE-404) vulnerability in Cesanta Mongoose. Its CVSS base score is 5.5 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 44th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-6985 is a vulnerability in Cesanta Mongoose versions up to 7.20, affecting the handle_opt function in the file /src/net_builtin.c within the TCP Option Handler component. The issue arises from manipulation of the optlen argument, which triggers an infinite loop, classified under CWE-404 and CWE-835. It carries a CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L), indicating a moderate-impact denial-of-service condition.
The vulnerability can be exploited remotely by unauthenticated attackers with network access and low complexity, requiring no user interaction or privileges. Successful exploitation causes an infinite loop in the affected component, leading to low-impact availability disruption, such as resource exhaustion on the targeted system.
Mitigation is available through upgrading to Cesanta Mongoose version 7.21, which resolves the issue, as confirmed by the vendor following early notification. A public exploit is available, detailed in a GitHub proof-of-concept at https://github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.md, with additional advisory information at https://github.com/cesanta/mongoose/releases/tag/7.21 and VulDB entries.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25661
Vulnerability Data
A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible…
more
to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the affected component is advised. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover missing or incorrect resource releases after code is written.
Flaw remediation processes identify and correct infinite-loop defects reported from testing or operations.
Requiring documented development processes and secure coding standards reduces introduction of loops whose termination conditions are unreachable.
Engineering principles can require explicit resource acquisition/release patterns that stop improper shutdown from being introduced.
Priority-based resource allocation limits the blast radius when released resources are not returned to the pool.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly include coding standards for correct resource allocation and release.
Runtime monitoring can detect resource exhaustion caused by improper shutdown or release.
Lifecycle management of assets can encompass proper resource release at end-of-life or shutdown.
Static analysis and vuln scanning during asset assessment can detect unreachable loop exits.
Capacity management helps surface leaks from unreleased resources but does not prevent the coding flaw.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can uncover infinite-loop conditions before release.
Including restart, recovery and media-handling instructions reduces the likelihood that resources or sensitive data will be left in an exposed or improperly released state after a failure.
Secure development life cycle mandates practices that can detect and prevent infinite-loop defects.
Application security requirements can specify loop-termination rules, indirectly reducing the weakness.
Secure coding standards directly address loop termination and prevent infinite loops.
Secure architecture principles encourage designs that avoid unreachable exit conditions.